This invention relates generally to an improved piezoelectric crystal oscillator circuit. It is particularly directed to the provision of a crystal oscillator for use in an electronic timepiece which has reduced power consumption.
Recently, wristwatches have been developed which utilize quartz crystal-controlled oscillators to provide a high frequency time standard signal.
In such timepieces, however, the self-contained power supply is of limited capacity. Therefore, it is advantageous to design the oscillator circuit such that its power consumption is minimal.
Some known embodiments of crystal-controlled oscillators utilized in wristwatches comprise a colpitts oscillator circuit with a crystal vibrator/resonator connected across the output and intput terminals of a phase inverting amplifier, and two condensers each connected between said output and input terminals and earth or a reference terminal. As seen from the prior art, however, the operation of this kind of crystal oscillator circuit gives rise in particular to such oscillation conditions which result in inefficient oscillator operation.
The prior art includes a number of crystal oscillator circuits such as is described in U.S. Pat. No. 3,855,549 issued Dec. 17; 1974 to Huener et al; U.S. Pat. No. 3,946,257 issued Mar. 23, 1976 to Yasukazu Kawamura; U.S. Pat. No. 3,935,546 issued Jan. 27, 1976 to Shimosuwa et al and U.S. Pat. No. 3,560,998 issued Feb. 2, 1971 to Walton.